This is a non-provisional application under 35 U.S.C. § 111(a) which claims priority from Japanese priority document 2005-278055 filed on Sep. 26, 2005, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink composition. In particular, the invention relates to an ink composition for inkjet recording, an ink set and a recording method.
2. Background Art
In recent years, following the diffusion of computers, inkjet printers are widely utilized for printing on papers, films, cloths, and so on in not only offices but also households.
The inkjet recording method includes a system of applying a pressure by a piezoelectric element and discharging droplets; a system of generating air bubbles in an ink by heat and discharging droplets; a system of using ultrasonic waves; and a system of sucking and discharging droplets by an electrostatic force. As an inkjet composition for such inkjet recording, an aqueous ink, an oil based ink, or a solid (melt type) ink. Of these inks, an aqueous ink is the mainstream in view of manufacturing properties, handling properties, odors, safety, and the like.
For coloring agents which are used for such an ink for inkjet recording, there are such requirements that they have high solubility in a solvent; that they can be subjected to high density recording; that they have good hue; that they have excellent fastness to light, heat, air, water or chemicals; that they have good fixing properties to an image receiving material and hardly cause oozing; that they have good preservability as an ink; that they are non-toxic; that they have a high purity; and that they are cheaply available. However, it is extremely difficult to seek coloring agents which are satisfied with these requirements in high levels.
Various dyes or pigments have already been proposed and actually used for inkjet recording. However, it is the present situation that a coloring agent which is satisfied with all of the forgoing requirements has not been discovered yet. In conventionally well known dyes or pigments to which a color index (C.I.) number is given, it is difficult to make hue and fastness as required for an ink for inkjet recording compatible with each other.
Under these circumstances, for the purpose of improving ozone resistance and light resistance of dyes, the present applicant has proceeded with development of a dye having an azo group on a heterocyclic group.
Such a dye is characterized in that the oxidation potential of the dye is high and that it is possible to design to improve ozone resistance and light resistance due to the promotion of association of a dye molecule.
However, since in preparing an ink, an ethylene oxide chain of a surfactant to be added in the ink and a heterocyclic ring in the dye molecule mutually act each other, an ability of the surfactant is lowered so that a surface tension of the ink cannot be reduced. For that reason, there were involved such problems that wetting of the ink on the surface of image receiving paper is deteriorated; that permeability of the ink is deteriorated; that drying properties of a printed matter are poor; and that deteriorations of image quality such as beading are observed.
That is, additives capable of improving drying properties of an image, controlling deteriorations of image quality such as beading and keeping good ozone resistance and light resistance have been desired.
Now, JP-A-5-339529 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) proposes a method of obtaining an image which is free from oozing at the time of color mixing by using an ink containing acetylene diol and an alkane diol.
JP-A-2004-35854 proposes a method of obtaining of an image which is free from beading, bleeding and feathering by using an ink containing 2,5-dimethyl-2,5-hexanediol and acetylene diol or an ethylene oxide adduct of acetylene diol.
Also, JP-A-2004-75766 proposes a method of obtaining an image which is free from beading, bleeding and feathering by using an ink containing 1-butanol and acetylene diol or an ethylene oxide adduct of acetylene diol.